PeterH

Related thread, especially

I would be wary of using a memento as a flower vase unless you are really sure that it will be fully waterproof. This requires a well-matched clay body, glaze and firing schedule.

+1 ... but my goto book source doesn't have anything cheap delivered to Malawi https://tinyurl.com/ff2mm2th

For a start just try UL Ferro frit in your search engine. For a start just try UK Ferro frit in your search engine.

If you are interested in glaze-over-glaze effects ... Basic "evening-class stuff", but a big test tile with a stripe of each of N glazes one way, overlain with a stripe of each glaze at right angles shows you the effects of all N glazes under/over all the others. I wouldn't try with N=60 though! ... a blank line in one direction [so an Nx(N-1) grid] shows single and double coverage of each glaze as well. The chief drawback is that you are only showing a spot of glaze fired on a smooth horizontal surface. Which probably isn't a big issue with tests for mosaic tiles. Still doesn't explore variations of glaze thickness (although the N+1 idea helps). PS Cannot find a picture at the moment, so I'll try to draw it. Underlined letters written on the test-tile. x/y indicates glaze x over glaze y. top A B C -- a b c A a/a a/b a/c B b/a b/b b/c C c/a c/b c/c ... here is an example with paints rather than glazes https://www.chrishilbig.com/review-golden-open-acrylic-paints/

A visual reminder that a little water expands into a lot of steam, rather quickly.

There is a user manual Page at https://device.report/manual/5720904 PDF at https://device.report/m/1c60d3e1d7c310b0b77655d1833e5aed8cbe06b41c530da1e376becee2620554_optim.pdf ... although it doesn't say much I expect that the RCD (residual current device) avoids the need for a user-replaceable fuse. (Although there might be a service-engineer-replaceable fuse hidden in the guts of the wheel somewhere.) Between them the two lights should indicate if power is reaching the wheel internals. I suspect that the stand-alone light indicates that power is reaching the box, and the light on the blue panel indicates if the RCD is letting it through. Can you say what lights you have on? from https://m.media-amazon.com/images/I/81Hi6FfkgqL._AC_SL1500_.jpg ... possibly from a different wheel.

This has been a learning experience. I've posted fresh ideas, new readers start there. PS Some of my previous posted ideas left here for completeness. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- A quick google failed to find a public domain manual. Although there was a site offering/purporting to have it, I'm always a bit suspicious of those. I assume that you've checked the fuse in the plug. It looks like it might have what we call an ELT (earth leakage trip) in the UK. from https://tinyurl.com/39sknyej Have you tried pressing what looks like a rectangular button on at the top RHS of the blue plate (while the power is off) it might reset the ELT. PS The "Leakage Protection Device" arrow seems to be pointing to a lamp, rather than the second button ELTs usually have. Can you confirm? ... found a better image (possibly from a different wheel) from https://m.media-amazon.com/images/I/81Hi6FfkgqL._AC_SL1500_.jpg Which looks like the rectangular button is a "test" button (trips the device). So how do you reset, is it just switching it on (which you are already doing)? So maybe I'm just saying make sure you switch it off then on again while the power is connected -and report what the lights do. PPS If you want to risk it (they might be clickbait) https://lb.manuals.plus/vevor/gcjx-series-pottery-wheel-machine-manual#axzz88NpegZVN https://device.report/manual/5720904 ... the second has some general advise on the page

From Neil's Links To Kiln Manuals, Wiring Diagrams, Repair Parts, Elements, Etc. The Paragon Kilns link leads to the circuit diagram for this part number https://eadn-wc04-7751283.nxedge.io/wp-content/uploads/S0743-1.pdf The 1/2amp fuse guards the transformer and the 24v controller it supplies. > As it was ramping up, about 45 min. into the firing, the internal fuse blew and there was a slight electrical fire smell. > I replaced to switch and the fuse blew again immediately upon plugging it in and turning it on. Naively, if the fuse now always blows at switch-on, I would suggest to the shop that they: - check the connections to the transformer - fully unplug the controller - and see if the fuse still blows - if the fuse doesn't blow check the voltages at the transformer between ORN/BLU, ORN/WHT and BLU/WHT. I would expect one of them should be the board's 24VAC? power supply. ... should help differentiate between the transformer (and its wiring) or the controller (and its wiring) being a problem.. But wait until one of the experts here confirms this is safe/sensible to do. PS I'm confused by the inverted-U shape shown on the diagram . It looks like it might be a link/strap but the transformer seems to only have seven terminals. https://paragonweb.com/home/transformer-2/

What model is it, there are several Caldaras. There should be a plate on it somewhere showing voltage, amps, watts, etc. Look for something like: Can you post a photo?

A google for dutch molds turns up several hits, including Catalogue at https://www.dutchmolds.nl/ ... but seems to be in Dutch.

There is a John's Noxema 117/5 at https://www.flickr.com/photos/glazes/40006967621 ... is this the recipe you use for the bottom glaze? PS Glazy has a Noxema https://glazy.org/recipes/6522 and a Noxema Blue https://glazy.org/recipes/2475

> And beside that how can I calculate it so that the object would get out of the setter in one piece? Note that the bone-china reference I sent used a one-time internal setter. As this was made of the same body as the pot being fired their shrinkage should be similar at all stages in the process. Obviously this isn't true for kiln-furniture style setters. As I've said previously, my concern with an outside setter is managing to keep the slot-ridges undamaged. > This would achieved with a fully closed mold I take that to mean you will be using a 2-piece mould, with the each piece defining one face of the cone. This mould would presumably also fully define the slot and its associated ridges. (Concerns about de-moulding the thin ridges and "dropping-out" a form with a slot.) I've done almost no solid casting, and worry that the thinness of your walls might be an issue when filling the mould.

How do you achieve the taper on the conical section, solid casting? ... and how thick is it at the rim?

I think that would give far better support, but handling the lip at the slot might be tricky.

I think that Tony Hansen's demonstration of the fallibility of ChatGPT is worth posting. ChatGPT is completely wrong about the cause of glaze crazing! https://digitalfire.com/picture/3159 ... a fine example of ignoring the elephant in the room. ... a fine example of ignoring the elephant in the room by ChatGPT PS It reminded me of a very old software engineering joke (1970s?). A man was been taken on a cross-country flight in a helicopter. During the flight the ground became completely covered in dense fog, and the pilot became lost. The eventually came across the top of a office tower sticking above the fog, and they hovered nearby. The man attracted the attention of somebody in the office and held up a placard saying "where are we?", and received the answer "in a helicopter hovering 60ft above the ground". The pilot said "OK I know exactly where we are, and set off towards their destination. Later he explained "the answer you got was technically correct and not the slightest help, so obviously we were at the Microsoft help centre whose location I know". Maybe ChatGPT is another help centre.

As I find pictures helpful in forming memories, not a dissimilar 2-stage process to that in Inlaid Slip Casting https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-article/Inlaid-Slip-Casting

A good question, and I'd like to know the answer. Presumably - in this case - it doesn't cause problems, although it may depend on the nature of the body and the firing range. Tony has always been very quick and professional in responding on the very few occasions I have draw attention to minor errors in his pages: e.g. misleading typos and wording. Maybe this is a case where you might want to take advantage of the $5 offer at the bottom of his web page.

Fine if you didn't have the slot and the form almost supported itself. But IMHO the area near the slot is going to droop unless it is supported over ~100% of its surface.

There is a little bit on one-use setters for bone china in Tempting Transparency https://ceramicartsnetwork.org/pottery-making-illustrated/pottery-making-illustrated-article/Tempting-Transparency# Ideas on the body to use for multi-use setters Bone China AntiWarp Setter test molds https://digitalfire.com/picture/3156 ... Tony Hansen uses a "kiln shelf" body for his setter L3693H1

But why in this glaze - and in Snowflake Crackle - do the cracks mainly appear to propagate parallel to the glaze surface rather than normal to it? There only seems to be two options: somehow the stress in normal to the glaze surface, or something is causing the propagating crack to change direction from normal to parallel to the glaze surface. ‡ PS The usually physical model for "fast" crack propagation just doesn't seem to apply here.† Hierarchical crack pattern as formed by successive domain divisions. I. Temporal and geometrical hierarchy https://tinyurl.com/3yu6wx6y † There is another model for "slow" cracks (where several may be propagating at the same time), for example mud drying. ... and the less relevant Hierarchical crack pattern as formed by successive domain divisions. II. From disordered to deterministic behavior. https://tinyurl.com/26w8ap4p ‡ Maybe there is some link with conchoidal fractures ( which explains how flint-knapping works)? † There is another model for "slow" cracks (where several cracks may be propagating at the same time), for example mud drying. PS Irrelevant to the present discussion, but an example of complex 3D cracks. Evolving fracture patterns: columnar joints, mud cracks and polygonal terrain https://royalsocietypublishing.org/doi/epdf/10.1098/rsta.2012.0353

I was looking at some of the colours in the original pictures and somewhat reluctantly came to the conclusion that they might indicate that the colour of the glaze varied with depth. Which of course some people have been saying for a long time about some copper reds. This made we wonder what would happen if you applied two differently coloured layers of snowflake crackle glaze. Would you get interestingly coloured patterns?

I think you've got it. Horizontal cracks within the glaze (acting as reflectors) would affect the colour (by reducing the distance light travels in the glaze) even if the colour is uniformly distributed in the glaze. The small amounts of colourants in copper-reds might also be significant. Snowflake Crackle https://ceramicartsnetwork.org/ceramic-recipes/recipe/Snowflake-Crackle Color The first thing I noticed when I did color tests with the usual colorants and opacifiers (copper carbonate, red iron oxide, chrome oxide, stains, Zircopax Plus, etc.) was that, as the color improved, the crazing ceased. This was because all oxides have expansion/contraction rates and adding them changed the CTE of the glaze enough to stop the crackle effect. I ran more tests with very low levels of colorants (under 1%), which kept the crazing yet still produced a nice color. PS Do you have any similarly fired pots which didn't show this effect? An ice-water stress test might be interesting. PPS I wanted to suggest that the relative freedom from cracks near the edge of the bowl was a significant clue, but couldn't word it right. So here is a picture of the effected -- with a smaller crackle size and hence smaller outside ring. I've been testing a Snowflake crackle glaze. Here it is over coloured slip https://www.reddit.com/r/Pottery/comments/8jjxxi/ive_been_testing_a_snowflake_crackle_glaze_here/

Interesting idea, do you have any specific approaches in mind? Lithium extraction from hard rock lithium ores (spodumene, lepidolite, zinnwaldite, petalite): Technology, resources, environment and cost http://en.cgsjournals.com/article/doi/10.31035/cg2022088 Lithium extraction from mechanically activated of petalite-Na2SO4 mixtures after isothermal heating https://www.sciencedirect.com/science/article/abs/pii/S089268752030114X ... full paper behind a firewall, but the relative solubilities of Na2SO4 & Li2SO4 suggests that Li2CO3 would precipitate out first.

Puzzled brainstorming. Wild idea for the colours, but not the cracks, fuming copper pooling in the bowl? I don't claim to fully understand copper reds. But fumed copper is presumably more likely to be present near the surface (and blue/green?), while there is a persistent argument that (some? all?) of the red is down below the surface. The Dual Mechanisms of Tin Oxide in Copper Red Glazes https://glazy.org/posts/168150 On second thoughts ... We seem to have a "paint-by-numbers" of regions: each of more-or-less uniform colour; with the sections delineated by cracks that almost certainly weren't there when the colours were formed. Large local differences in composition might explain the positioning of the cracks, but it's hard to see how that could happen. Could it be caused by differences in surface texture/crystallisation? That might add surface reflections (colour), and also influence crack initiation/propagation (position). Any chance of a specular-reflection free image of the same location? PS >And, to note, the pieces rang like a bell out of the kiln. Can you remember if they had the angular colour pattern before they cracked? Yes - the colour differences are controlling the position of the cracks? Surface texture influencing both? No - the cracks are causing the colour differences? Is it conceivable that the release of stress caused by the crack changes the surface texture?